204 FOREST ENTOMOLOGY. 



species of this family is often mistaken for a scale viz., the fringed 

 aphis (Gerataphis latanice), known to horticulturists as the "black- 

 seed scale" : it occurs on palms, orchids, &c. (see fig. 194). 



The Psyllidae very much resemble the Aphididae in general appear- 

 ance, but their legs are formed for leaping. The wings are clear, the 

 antennae conspicuous, long, nine- or ten-jointed, and the eyes large and 

 prominent. The tarsus is two-jointed. 



In general appearance the Aleyrodidae are the nearest approach 

 to the scale -insects, more especially so in their nymphal or pupal 



stages. Their bodies are of an 

 ivory-white colour, scaly-looking 

 in appearance ; both sexes are 

 winged, and the tarsi two-jointed. 



Fig. 195. Scale-like secretion of Aleuro&es Thev often deposit a Scale - like 



on leaf of tomato. J r 



secretion on plants (see fig. 195). 

 Aleyrodidae are found on tomatoes, &c, in greenhouses, and on ivy, 

 lime, and hazel in the woods. 



The closely allied Coccid^e are broadly distinguished from the other 

 families of the Homoptera just referred to by the following character- 

 istics viz. : In the females by being naked (Lecanium), clothed partly 

 with secretion and partly with moulted skins {Diaspince), or clothed 

 with white meal-like secretion (Dactylopius), and with wax-like plates 

 (Orthezia). The tarsus in all the British species but one 1 is composed 

 of a single joint ; there are also two foreign genera in which the tarsi 

 are fooo-jointed. 



The larvae are minute, and very active when young, usually naked, 

 and the sexes are inseparable in the first larval stage. 



The female undergoes a semi-complete metamorphosis, is apterous 

 in all stages, has generally a well-developed rostrum, and, according to 

 the genus, the legs may be present or absent. 



The adult male undergoes a complete metamorphosis, and may be 

 winged or apterous. It has no mouth or feeding-organs, but possesses 

 six legs, eyes, and antennas. 



It is important to bear in mind that both sexes secrete a varying 

 quantity of waxy, horny, mealy, or resinous substances for the forma- 

 tion of their shield-covering or scale, and that these secretions or 

 coverings vary in form and colour. In fact, those differences are so 

 1 Exceretopus formiciticola, Newst. 



